This invention relates to a tool support and guide system for effecting rapid end preparation of tube ends of boiler tube panels and, more particularly, to a tool system for preparing ends of tubes adjacent a removed boiler tube panel section to enable a replacement panel section to be installed by welding, including a method of using the tool system.
The tube panels with which the tool system of the present invention is used are found, for example, in electrical power generating plants and in steam generating boilers found therein. However, the invention has application in any type of heat exchanger system using tube panels of this type.
The tube panels of concern are generally found arranged in vertical or inclined walls and include metal tubes joined together by metal membranes or webbing welded to adjacent tubes or by comparable narrow metal interconnecting strips. The tubes are customarily made of steel and are subject to corrosion in the generation of steam therein as they provide a continuous fluid circuit within the boiler. Because of their massive size, it has become accepted practice to remove rectangular sections of tube panels when tubes in a given area become damaged or ruptured and to insert as by welding a replacement section of panel. To replace an entire panel or wall section would be too disruptive to the operation of the power generating station and much too costly in actual practice.
Accordingly, some of the early attempts to deal with this problem involved the use of hand held tools or cutting torches to cut rectangular sections from the tube wall which included the damaged portions. This was a lengthy, inefficient process, and it was soon found that the dimensions of the removed panel section had to be more precise than could be obtained from hand held tools in order for the replacement section to be fitted properly, without extensive labor.
Thus, it became evident that guide means would be required to guide the cutting operation and to remove sections whose dimensions were known very precisely so that a replacement section could be prefabricated and reinserted in a short period of time.
One such apparatus for replacing damaged tube sections is disclosed in U.S. Pat. No. 4,633,555 issued on Jan. 6, 1987 to Legge. In this device, a saw is mounted on a guide means for slidable movement thereon. With the aid of this guide it is possible to cut a straight line through the tubes that are parallel to the guide at a predetermined distance from the guide. By repositioning the guide on the tube wall, it is possible to cut and remove a rectangular panel section with straight cut lines.
This patent also discloses an end preparation tool (termed an "end prep" tool in the trade) mountable on the guide for movement therealong so the end prep tool can be located adjacent the end of each cut off tube for machining a precise bevel thereon in preparation for welding of a replacement tube panel in the removed section.
The system according to the above-mentioned U.S. Pat. No. 4,633,555 does not provide a means for cutting the webs between the tubes of the tube panels and moreover is specifically designed to enable this saw to slide along the guide during the cutting procedure.
Another system for cutting out damaged panel tube sections is disclosed in U.S. patent application Ser. No. 213,939, filed June 30, 1988 naming W. H. Astle as inventor and entitled, "Panel Saw Apparatus" and assigned in common with the present invention. The aforementoned patent application is incorporated herein by reference and describes a panel saw adapted to be guided by a rail means temporarily attached to a tube panel whereby a straight line cut through the panel can be carried out by a series of plunge cuts through the tubes of the panel while the saw is braked relative to the guide rails during each cut.
It has been observed that it would be highly desirable to provide a single adapter system usable with the temporarily installed guide rail described in the aforementioned U.S. patent application Ser. No. 213,939 that would enable mounting of a membrane cutting saw as well as an end prep tool so that, without removing the guide rail, the membranes between the tubes of the panel could be severed and then, with a minimum of tool changeover, the ends of the tubes could be prepared as by bevelling for installation of the replacement tube panel.